Senator Daniel Inouye of Hawaii has died. He was 88. He was the president pro tempore of the Senate, an honor held by the most senior member of the majority party and a position that stands third in the presidential line of succession. Inouye died today at Walter Reed hospital outside Washington, D.C., from complications of respiratory disease. Next month, he would have marked his 50th anniversary in the Senate, having taken the oath for the first time in 1963.

Joining me to talk about the senator's career is NPR senior Washington editor Ron Elving. And, Ron, Senator Inouye was far from the household name outside of Hawaii. What made him so powerful in the Senate?

RON ELVING, BYLINE: Melissa, you have to start with seniority. Senator Inouye had served longer than anyone in the history, except the late Robert C. Byrd who had maybe a year on him, and secondly, had go to the key committee assignments that the senator had. He was chairman of the Appropriations Committee. In recent years, that is the summit, if you will, the pinnacle power in the Senate, and before that, had been subcommittee for Defense, chair for a number of years. And, of course, he had also been chairman of the Commerce Committee for a while. And some of us remember him as the co-chairman of the Iran-Contra Committee back in 1987 and part of the Watergate Investigating Committee in 1973.

Beyond that, he had tremendous alliances with senior members in both parties, especially on Appropriations. He was fearfully loyal across party lines, and an old-school gentleman, if you will, somebody who saw his duty as a senator to be in the Senate and not in TV studios or on the presidential primary hustings.

BLOCK: And, Ron, a special significance to Senator Inouye being at Walter Reed at the end of his life, he was a decorated veteran.

ELVING: He was, indeed. He was associated closely with the U.S. Army and the Veterans Administration back for 70 years, back to when he was an 18-year-old who volunteered to fight in World War II. This is Senator Harry Reid, the current Senate Majority leader, on the floor today remembering some of the key points in Senator Inouye's life.

ELVING: You know, the senator was born in Honolulu to a family of Japanese immigrants. And he joined a unit, the 442nd Regimental Combat Team, which was a special unit of soldiers who are second-generation Japanese Americans who fought in Italy and in France. And he did lose his right arm there to a German grenade and spent 20 months in military hospitals thereafter and was, much later, awarded the Medal of Honor for that service.

BLOCK: And, Ron, Senator Inouye, as we said, in the Senate for about 50 years; in Congress since Hawaii became a state.

ELVING: That's right. He was really the definition of an institution in Hawaii politics, all the way back to the Territorial Legislature in the 1950s and then when Hawaii becomes a state in 1959. He is the first member of Congress from Hawaii, and then a few years later, elected to the Senate, 50 years ago this fall by 78 percent and pretty easily re-elected since.

BLOCK: And, Ron, does Senator Inouye's death shifts the power structure of the Senate in a meaningful way?

ELVING: Not in partisan terms. The Democratic governor of Hawaii, Neil Abercrombie, is expected to nominate a Democratic replacement. And the job of president pro tempore will go to the second most senior Democrat in the Senate, Patrick Leahy of Vermont - a new generation, if you will. Patrick Leahy is 72. And we may also see something of a change at the Appropriations Committee in percentage and in style.

BLOCK: OK, Ron, thank you.

ELVING: Thank you, Melissa.

BLOCK: That's NPR's Ron Elving. We were talking about the Democratic Senator Daniel Inouye of Hawaii who died today at age 88. Transcript provided by NPR, Copyright NPR.